Various methods of pasteurizing food products have been developed over the years. Most of the commercial processes are for pasteurizing liquid/semi-liquid food products, such as juices, pastes, relishes, sauces, and other foods, involve heating the product to a process temperature above certain temperature and holding it for a scheduled process time and then rapidly cooling the product prior to packaging. Unfortunately, methods involving high heat such as this can sometimes damage the food product and reduce its quality. For example, flavors may be reduced, desirable colors may be lost, and nutritional value may diminish. Thus, while conventional thermal processing has become the predominant commercial pasteurization method, the overall quality of the food products would be greatly increased if the drawbacks of high heat processing were reduced or eliminated.
A number of processes have been developed and proposed related to non-thermal methods of pasteurization. These processes typically use ultra filtration, ozonation, ultraviolet light, irradiation, high hydrostatic pressure (HHP) and pulsed electric field (PEF) discharge. Other non-thermal technologies useful for this purpose include high voltage arc discharge, oscillating magnetic field discharge and ultrasonic discharge.
For example, in U.S. Patent Application Publication Number 20030026877 discloses a method and apparatus for sterilizing a liquid that has pathogens living in the liquid. Typically, the liquid with living pathogens is placed in a reaction volume, and a non-thermal plasma is generated within the reaction volume to kill at least a portion of the pathogens within the liquid to achieve sterilization.
Another example can be found in U.S. Patent Application Publication Number 20040016892. Briefly, the '892 Application teaches an improved electronic pasteurization method and system. This improved electronic pasteurization system includes a coupled accelerator and a treatment station. The coupled accelerator includes a coupled multiplier supply (CMS) having a mechanical drive system and power modules. The mechanical drive system supplies mechanical power to the power modules, which convert the mechanical power into electrical power that provides stepped-up power to the accelerator column.
Another example can also be found in U.S. Patent Application Publication Number 20040191374 by Weng, et al. Briefly, Weng discloses a multi-stage system and method for pasteurizing food products that includes a first processing unit configured to receive the food product and apply an amount of non-thermal energy treatment to the food product which is effective to inactivate enzymes. A second processing unit configured to receive the food product from the first processing unit and to reduce the population of potentially harmful microorganisms to a level that is not harmful to consumers. The second processing unit may also include a concentration unit, which removes water from the food product to produce a concentrated form of the product. The first processing unit may have a high voltage-arc discharge unit, a non-thermal pulsed electric field unit, an oscillating magnetic field unit, or an ultrasonic unit.
Yet another example is shown in U.S. Pat. No. 7,373,254 issued to Pierce. Briefly, Pierce discloses a process of selectively exposing matter to a specific wavelength of electromagnetic energy in sufficient flux density per wavelength to cause or promote a desired effect. The process includes destroying, disinfecting, denaturing, disinfesting, disrupting, or dehydration of the substances present. The '254 patent also relates to subjecting matter, which may contain a mixture of substances, to electromagnetic energy, in concurrence with its spectral properties to exploit the spectral differences within the substance or within a mixture of substances. Energies are applied to cause wavelength-dependent reactions resulting from differential absorption; this additional applied energy manifests itself in changes, or quantum transitions, in the vibrational, rotational, magnetic, and electronic states of the molecules. Generally, the process uses wavelengths from one light second to ten electron volts, or wavelengths with energy levels less than that of ionization.
Finally, U.S. Pat. No. 7,187,752 entitled “Product irradiator for optimizing dose uniformity in products” issued to Kotler discloses an apparatus and method for irradiating a product or product stack with a relatively even radiation dose distribution. The apparatus includes a radiation source, an adjustable collimator, a turntable capable of receiving a product stack and a control system capable of adjusting the adjustable collimator to vary the geometry of the radiation beam as the product stack is rotated in the radiation beam. Kotler also discloses modulation of the radiation beam energy and power and that a low dose uniformity ratio in the product stack is achieved by varying the angular rotational velocity of the product stack in a radiation beam.
However, almost all of the above mention references suffer from multiple drawbacks. For example, most existing technologies cannot deliver uniform dose of energy. When the energy dose is too high, the object (e.g., food products) may be damaged, and if the dose is too low, insufficient sterilization can occur. Furthermore, shape of the object causes additional problems because irregular shapes (e.g., round or that of a carcass) contribute more towards non-uniform energy dose distributions by displaying hard to reach angles for a typically irradiation to reach.